This invention relates to a method for realizing an uplink outer loop power control carried out as a part of transmission power control in a third-generation mobile system.
Uplink (UL) inner loop power control and uplink outer loop power control are carried out as transmission power control in a third-generation (3G) mobile system and are defined in 3G TS25.401 UTRAN Overall Description in outline.
The third-generation mobile system generally includes a radio network controller, a node connected to the radio network controller by a wire or a signal transmission line, and a user equipment which is typically a mobile station. The node is typically a base station and has a service area. Within the service area of the node, the user equipment can communicate with the node by radio communication or wireless communication.
In the third-generation mobile system, the uplink inner loop power control and the uplink outer loop power control are carried out as the transmission power control in order to suppress a radio interference and to obtain a high communication quality.
In the uplink inner loop power control, the user equipment transmits a signal to the node by the use of an uplink dedicated physical control channel for the user equipment. The node receives the signal as a desired wave from the uplink dedicated physical control channel. In this event, the node unavoidably receives an interference wave from other channels. When the node receives the signal, the node measures a ratio of a power of the desired wave to another power of the interference wave as a measured SIR (Signal to Interference Ratio) and compares the measured SIR with a reference value which is called a target SIR in the art. When the measured SIR is smaller than the target SIR, the node transmits, by the use of a downlink dedicated physical control channel for the user equipment, to the user equipment an increment command indicative of increment of a transmission power of the signal to make the user equipment increase the transmission power of the signal. When the measured SIR is larger than the target SIR by a predetermined amount or value, the node transmits, by the use of the downlink dedicated physical control channel for the user equipment, to the user equipment a decrement command indicative of decrement of the transmission power of the signal to make the user equipment decrease the transmission power of the signal.
In the uplink outer loop power control, the radio network controller updates the target SIR of the node into a new target SIR which is a new reference value. In order to update the target SIR of the node, it is necessary that the radio network controller knows a radio condition around the node by receiving a report transmitted from the node. The report represents whether the radio condition has an excessive quality or a degraded quality. In order to produce the report, the node has to measure a block error ratio (BLER) of an uplink signal from the user equipment for a predetermined time duration. The node transmits to the radio network controller a measurement result of the block error ratio (BLER) as the report to make the radio network controller update the target SIR of the node into the new target SIR in accordance with the report. However, the radio condition around the node inevitably change with time. The radio condition is very likely to have a different condition at the instant when the radio network controller updates the target SIR of the node into the new target SIR in accordance with the report received from the node.
In particular, it is defective in that the node consumes a long time in measurement in order to judge that the radio condition has the excessive quality. In order to judge that the radio condition has the excessive quality, the node has to measure a predetermined number of measurements and to compare the measured result with a threshold value for the excessive quality.